Experimental Study Of Post Arrays On Stainless Steel By Wire Electrochemical Machining

Compared with the ordinary surface,the superhydrophobic surface shows excellentsuper-wettability.When the droplet impacts the surface at a certain speed,it will promote rapid drop detachment,which can effectively reduce the liquid-solid contact time.So,it has a wide application prospects including anti-freezing and frosting,non-destructive transfer of liquid and self-cleaning,having attracted the attention of mangy scholars and experts.In recent years,studies show that a super-hydrophobic surface with a special structure,the liquid-solid contact time can be further reduced,having a wider application potential in anti-freezing.At present,structures having such characteristics are mainly post or tapered arrays and the single structure has a less size and a larger high-apect-ratio,which generally rely on expensive equipment and complex process during the preparation process.In this paper,wire electrochemical machining is used to fabricate post arrays with rounded corner on stainless steel substrate.After superhydrophobic modification,the solid-liquid contact time can also be reduced when the droplet impacts on the post arrays with rounded corner.The main research work and results of this paper are as follows:(1)The experiments of machining process were carried out with wire electrochemical machining system.Firstly,the main factors such as machining current,feedrate of wire electrode,electrolyte concentration and flowrate of electrolyte that influence the morphology and width of slit in the machining process were investigated.Then,based on these,a multi-scale composite rough structures were fabricated on stainless steel substrate by WECM with a optimal parameters.After being modified by the fluoroalkylsilane to reduce the surface energy,superhydrophobic post arrays with high water static contact angles were produced.Finally,the static contact angle of superhydrophobic post arrays with different size was investigated.(2)Based on the above experimental results,a controllable machining study of the post array was conducted.Firstly,the influence of machining current and feedrate on the top width of slit was investigated under a given initial gap.It is proved that post arrays with rounded corner can be fabricated by changing the machining current and feedrate;Secondly,the influence of the center-to-center spacing and machining depth on the rounded corner structure of slit was studied,which proved the center-to-center spacing and machining depth having little influence on the forming of rounded corner structure of slit.Then,for the phenomenon of instability in machining process,the SEM and EDS images of the wire cathode wereanalyzed.The results indicated that the requirement for the flushing system is higher when the real machining length is large.Otherwise,the electrolytic products are difficult to be carried away from the machining slit in time and greatly affect the normal machining process.Finally,post array with rounded corner of different shapes is prepared.(3)The post arrays with rounded corner were fabricated with WECM.The center-to-center spacing and the height of post are 500 ?m and 600 ?m,respectively.After being sprayed superhydrophobic nanoparticles,superhydrophobic post arrays with rounded corner were obtained.When 4.1 ?L droplet was dropped on the superhydrophobic post arrays at a height of 50 mm,pancake bouncing was observed by the high speed camera and the liquid-solid contact time was shortened to 3.5 ms,which is greatly reduced compared with superhydrophobic surface.Also,it proved that using superhydrophobic post arrays with rounded corner structure had reducing contact time effect.